Fiber optic communication networks are experiencing rapidly increasing growth in capacity. This capacity growth is reflected by individual channel data rates, scaling from 10 Gbps (gigabits per second), to 40 Gbps, to developing 100 Gbps, and to future projections of 1000 Gbps channels and beyond. The capacity growth is also reflected by increasing total channel count and/or optical spectrum carried within an optical fiber. In the past, optical channels were deployed with a fixed capacity in terms of bandwidth as well as a fixed amount of overhead for forward error correction (FEC). For example, in a conventional system deployment, channels are deployed at 10 Gbps or 40 Gbps (plus associated overhead for FEC). These channels are designed to provide fixed data throughput capacity of 10 Gbps or 40 Gbps. Moreover, the performance limits of these channels are established assuming that the system is operating at full capacity, with all the optical channels present. The first in channels will operate in much more benign condition and have significant extra margin available. This margin is not utilized until much later in the lifecycle of the system. For example, a single wavelength deployed on a new optical line system could have more than 10 dB of excess margin that is not currently utilized (without adding new hardware). This unused margin can be considered wasted and forcing the system to operate in a non-cost effective way. If this extra margin could be utilized, even in a temporary way, to enhance data throughput of the modem, for example, the economics of the system would be significantly improved.
Of note, next generation optical modems are equipped with the capability to support variable data throughput applications. Moreover, this capability will be provisionable. Therefore, depending on the opportunity, it would be advantageous to provision a modem at a higher data throughput when the extra margin is available on new and low channel count deployments, usage of these next generation modem will allow to mine and use this excess margin and wasted capacity without requiring additional hardware. However, this excess margin could disappear as the channel counts approach full fill.
It would be advantageous to have systems and methods for determining what margin exists in an optical network. Conventional systems perform optimization mainly without the benefits of actual margin measurements. A simplified approach optimizes performance and determines margin based on fixed channel power targets into different fiber types, and this can be a calculation, such as from external tools. Other approaches can use Optical Signal-to-Noise Ratio (OSNR) optimization, either measured by a system using Optical Performance Monitors (OPMs) or estimated through modeling. The main limitation of these approaches is they are not able to take advantage of the existing knowledge of the performance of the data-bearing channels. This can be used to improve system resiliency or to increase capacity. One specific unknown in these systems is the contribution of non-linear noise to the performance of the channel.